The present invention relates to a method of manufacturing stainless steels. More particularly, the invention is directed to the method of manufacturing chromium steels having a low carbon content from starting materials which include chromium oxide.
As is presently known in the art, chromite (chromium ore) is used in the manufacture of chromium steels and various multi-step processes are used for this purpose. For example, there is known a three-step process in which the ore is reduced in a ferro-chromium furnace to obtain a suitable chromium alloy which is then cast into large bars and fed into an arc furnace where it is mixed with scrap to give a basic melt. This is then tapped over into an argon-oxygen-degassing (AOD) converter where it is refined to stainless steel with a mixture of oxygen gas and inert gas (e.g. argon). Such conventional processes require expensive equipment, are laborious and also consume a considerable amount of energy.
The present invention also represents an improvement with respect to the method disclosed in U.S. Pat. No. 4,072,504 wherein there is generally disclosed a method of reducing metal oxides by pre-reducing the oxides with the reducing gases released during final reduction.